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Inside of the Super-Kamiokande Proton Decay Detector at the University of Tokyo before it was filled with water (from Kamioka Observatory, ICRR, University of Tokyo, via greg.org).

Inside of the Super-Kamiokande Proton Decay Detector at the University of Tokyo before it was filled with water (from Kamioka Observatory, ICRR, University of Tokyo, via greg.org).